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Pyrophyllite from
Saint Clair, Schuylkill Co., Pennsylvania, USA

Classification
Species:Pyrophyllite
Formula:Al2Si4O10(OH)2
Comments:from the reference: "Exceptionally preserved plant fossils from St. Clair, Pennysylvania, have long been part of museum and private collections. Fossil fern leaves and stems from the underclay of the Buck Mountain Coal (Reading Anthracite Company quarry), lowest Llewellyn Formation (late Pennsylvanian, Virgilian), combine outer layers of coalified organic material (phytoleim) with strikingly white kaolinite, quartz, and the low-grade metamorphic mineral pyrophyllite in the interior. The surficial dark, coalified material appears to preserve the dense outer layers (cuticle, epidermis, and palisade layer) and some cell walls of fossilized leaves. XRD spectra of separated phytoleim contain graphite peaks. Raman spectra with peaks near 1600 and 1320 cm-1 indicate that the phytoleim is composed of disordered graphitic material. ID/IG ratios from ca. 0.3 to 0.45 are consistent with greenschist facies metamorphic conditions forming the anthracite coal. The interior pyrophyllite is highly crystalline, with large crystals often oriented perpendicular to leaf surfaces. Hydrothermal formation of pyrophyllite requires relatively limited groundwater flow conditions and temperatures between ca. 275 and 350°C. Although many fossil leaves are compressed, some are near original thickness. We infer that the remains were replaced prior to significant burial and compression of the sediment by an early-forming mineral phase, possibly pyrite, which was in turn replaced by kaolinite and then pyrophyllite at higher temperature and pressure. Woody structures such as cuticle and veins, which had resisted replacement by the initial low temperature phase, were coalified at higher temperatures."
Colour:white to tan
Significance:Unusual or interesting association, relationships with other species, pseudomorphism etc. - see notes.
Abundance at site:Common
Confirmation
Validity:Believed Valid
References
References:Stephen Peterson, George H. Myer, Barbara S. Grandstaff, and David E. Grandstaff (2011) A multistage model of preservation in fossil plants from the Llewellyn Formation (Pennsylvanian), St. Clair, Pennsylvania, USA. Paper no. 173-5, 2011 GSA Annual Meeting in Minneapolis (9-12 October 2011)
Data
Mineral Data:Click here to view Pyrophyllite data
Locality Data:Click here to view Saint Clair, Schuylkill Co., Pennsylvania, USA
Nearest other occurrences of Pyrophyllite
16.6km (10.3 miles) Centralia, Columbia Co., Pennsylvania, USA
73.2km (45.5 miles) Sullivan Trail Coal Company Mine, Pittston, Luzerne Co., Pennsylvania, USA
 
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